No consensus has developed on exactly where this find fits into the human family tree (or, more appropriately, “family bush”), but, even if it is a hominin, it is highly unlikely to be a direct ancestor of , then, emphasizes an evolutionary pattern that seems to have been a characteristic of the tribe Hominini from the very start—a pattern that aligns it with what is observed in most other evolutionarily successful groups of mammals.
Human evolution, it appears, has consistently been a process of trial and error.
In contrast, Lucy’s skeleton is 40 percent complete and dates to about 3.2 mya.
Lucy’s pelvis is more humanlike, and the design of her knee joint suggests that she walked upright in a manner similar to that of modern humans.
Fossils found since the early 1990s have begun to hint at just how complex the hominin bush was in the three million years or so following the time of , both known from South and East African sites.
This early radiation (diversification) of hominins, of which the latest survivors lived as recently as about 1.5 mya, made for a rather motley assortment.
The most remarkable aspect of this skull is the broadness and flatness of its face—something previously associated with much more recent hominins—in conjunction with a smaller, ape-sized braincase.
A variety of incomplete or broken fossils from the period between about 2.5 and 2.0 mya have been placed in the category of “early .
All these features would have made them agile upright foragers among tree branches, where they presumably sought food by day and sheltered at night even though they moved on two legs while on the ground.
The environments in which these early hominins lived suggest that (1) they were still comfortable in the forest and (2) they were largely active at the forest edges and in the woodlands where the forest graded into more open savanna—a type of habitat that was expanding in their African homeland after about 7 mya as climates became drier and more seasonal.
These fossils, along with the slightly older trails of footprints found at Laetoli, Tanzania, prove that early hominins were upright bipeds when on the ground.
However, they also retained many reminders of their tree-dwelling ancestry, especially their rather long arms, short legs, narrow shoulders, and long grasping extremities.